Although the elements which comprise 'protective immunity 'to HIV- l infection remain to be defined, a number of recent findings have greatly strengthened the contention that CD8+ effector cell populations play a pivotal role in the establishment and maintenance of the asymptomatic phase of illness. Basic studies aimed at augmentation of existing cellular reactivities in HIV-l infected patients could form the basis for future therapeutic approaches aimed at prolongation of the asymptomatic interval. The overall goal of this application is to examine in detail two distinct forms of cellular anti-HIV-l immune reactivities which are likely components of 'protective immunity'. The first portion of these studies is directed toward antigen-specific activation and expansion of HIV-specific CTLp present in infected patients. The mainstay of these cellular activation studies will be an in vitro stimulation (IVS) strategy developed in the context of the previous application which is based on the use of transient expression vector system consisting of recombinant, replication-incompetent avipox/HIV- l constructs. Different forms of antigen presentation will be evaluated with respect to CTL activation, including the use of dendritic cell populations as well as poxvirus/B7.2 vector-infected PBMC. Various cytokines will be assessed for their capacity to support antigen-specific activation and expansion of HIV- l specific CTL. Quantitation of the relative effects of these parameters on CTLp activation will be accomplished by determination of effector cell frequencies using limit dilution analysis (LDA). The avipox-based activation strategy will also be utilized to determine the relative frequencies of env-, gag-, pol-, and nef-specific CTL during the asymptomatic phase as well as late stage disease. The second portion of the proposed studies will be dedicated to non-cytolytic CD8+ cells which have the capacity to suppress HIV-l replication. These studies will examine several highly relevant parameters of virus suppression through the use of clonal populations of virus-suppressing CD8+ cells derived from HIV-l infected patients. Approaches will be designed to characterize different clonal populations with respect to patterns of cytokine production, specificity of viral inhibition, and various aspects of transcriptional inhibition. Attempts will be made to examine possible virus-suppressive responses present in HIV-1 vaccine recipients. Lastly, molecular approaches will be utilized to examine CD8+ cell-mediated virus- suppression in the context of host cellular transcription elements. Collectively, these efforts should contribute greatly to our current understanding of lymphocyte biology as it relates to virus-specific CTL activation and non-cytolytic virus suppression. The proposed studies will identify critical elements required for future immune-based therapies involving antigen-specific CTL and virus-suppressive CD8+ cells as therapeutic modalities.